Downloading binary file in javascript (node) from github

I am trying to download a file from github, but I am getting inconsistent sizes than if I download the raw file from github, I am using the download_url that I get from the directory listing from github. My code is:

async function getWaveDataFile(url) {
    try {
        const token = 'github_pat_personal-acess-token';
       
        
        const instance = axios.create({
            baseURL: url,
            timeout: 5000,
            headers: { Authorization: 'token ' + token },
        });
        console.log("axios Created BaseURL", instance.defaults.baseURL);


        const res = await instance.get();
        
        return res.data;
    } catch (err) {
        console.error('GG', err);
    }
}

I get binary data result from this, but if I save it to a file the size is inconsistent with a manual file download.

Any help with this would be much appreciated